Embodiments of the present invention relate to a polyamide water treatment separation membrane and a manufacturing method thereof, and more particularly, to a polyamide separation membrane having improved antifouling properties by forming a coating layer including specific compounds on a polyamide layer, and a manufacturing method thereof.
Osmosis occurs when two solutions of different concentrations are separated by a semipermeable membrane, and solvent flows from a solution having a lower concentration of solute through the membrane to another solution having a higher concentration of solute. The pressure applied to the solution having the higher concentration of the solute by the movement of the solution is known as osmotic pressure. When an external pressure higher than the osmotic pressure is applied to the higher concentration side, the solvent may move from the solution having the higher concentration of the solute to the solution having the lower concentration of the solute. This phenomenon is known as reverse osmosis. By using the principle of reverse osmosis, various salts and organic materials may be separated by the semipermeable membrane by using a pressure gradient as a driving force. A separation membrane is used for separating materials on the molecular level, removing salts from saline water and seawater, and providing water for domestic, commercial and industrial uses using the reverse osmosis phenomenon.
A polyamide membrane is an example of such a water treatment separation membrane. The polyamide membrane is manufactured by forming an active polyamide layer on a support having pores with a small pore size. The support having pores is formed by forming a polysulfone layer on a non-woven fabric. The polysulfone-coated non-woven fabric is then impregnated with an aqueous m-phenylenediamine (mPD) solution to form an mPD layer and the mPD layer is impregnated with a trimesoyl chloride (TMC) organic solution so that the mPD layer contacts the TMC to allow interfacial polymerization. As a result, a polyamide layer is formed on the support having pores.
Some commercial applications may require certain conditions to be met by a separation membrane. One of these conditions is a high salt rejection rate. A commercially required salt rejection rate for a water treatment separation membrane may be 97% or above with respect to brackish water. Other significant properties include high flux properties by which a relatively large amount of water may be transmitted under a relatively low pressure. In general, the preferred permeation flux of a membrane is known to be 10 gallons/ft2-day (gfd) under a pressure of 800 psi for sea water, and 15 gfd or above under a pressure of 220 psi for saline water.
Recently, prevention of fouling of the separation membrane has been recognized as a potential area for improvement along with other characteristics, such as the salt rejection rate and the permeation flux. When a membrane is fouled, floating materials or dissolved materials may be attached to the surface of the membrane. When fouling occurs, permeation flux may be decreased due to the absorption and growth of microorganisms on the surface of the membrane. This may cause secondary pollution, such as forming a biofilm on the surface of the separation membrane. Since a polluted separation membrane has decreased permeation properties, frequent corrections of the pressure may be necessary to maintain a constant permeation flux. When the fouling of the membrane is severe, a cleaning process may be required.